The present invention relates to a rolling mill, and more particularly to an on-line roll grinding apparatus installed in a strip rolling mill. Especially, the invention relates to an on-line roll grinding apparatus for effectively grinding rolls on-line without being affected by influences of vibration of work rolls.
Generally, when slabs are rolled by work rolls of a strip rolling mill, there occurs a periphery difference between the rolling zone and the unrolling zone because only the former is abraded or worn away. This imposes restrictions upon the rolling operation when rolling slabs of different widths. To solve that problem, there have been proposed various techniques and control methods in relation to on-line roll grinders.
For example, according to "Development of On-Line Roll Grinders", Mitsubishi Giho, Vol. 25, No. 4, 1988 and JP, U, 62-174705, a plurality of cup grinding stones are arranged along one work roll and mounted in a one-piece frame, the frame being always moved in its entirety over a certain range, and the cup grinding stones are not positively driven to rotate but passively driven (dragged) with the aid of torque of the work roll, thereby grinding the entire surface of the work roll (hereinafter referred to as first prior art).
Also, JP, U, 58-28705 discloses a technique wherein one roll grinding unit is disposed for one work roll, contact rolls serving as position sensors are held in contact with neck portions at both ends of the work roll on the side thereof opposite to the roll grinding unit, the position sensors detecting an offset of the work roll axis, and a shifting device is controlled to move a grinding wheel following the detected offset (hereinafter referred to as second prior art).
Further, "On-Line Constant Pressure Grinding for Work Rolls", Proceedings of 1992 Spring Lecture Meeting of Precision Engineering Society of Japan, reports an experimental result of forming an abrasive layer of a cup grinding stone using abrasives of cubic boron nitride (CBN), arranging a spindle of the grinding stone substantially perpendicularly to the axis of a work roll, and grinding the work roll (hereinafter referred to as third prior art).
In addition, JP, U, 58-28706 and JP, U, 62-95867 disclose a technique that a cup grinding stone arranged substantially perpendicularly to a work roll is mounted to a spindle slidably in its axial direction, and the grinding stone is axially supported at its backside by an elastic body directly or via a boss, thereby absorbing vibration of the work roll (hereinafter referred to as fourth prior art).
According to JP, A, 61-242711, one roll is ground by using only one grinding stone based on the same grinding method as in the above first prior art, and a grinding surface of the grinding stone is reversed near the axial center of the roll for grinding the entire roll length (hereinafter referred to as fifth prior art).
Meanwhile, in relation to an on-line roll grinder for use with a roll crossing mill wherein a strip is rolled by a pair of upper and lower work rolls with their axes inclined in a horizontal plane from a direction perpendicular to the rolling direction, JP, A, 61-88907 discloses one example in which a grinding member is moved in a horizontal plane following a work roll. More specifically, a frame housing the grinding member therein is provided at both transverse ends with a fixed cushion and a free cushion held in abutment with work roll chocks, these two cushions serving to make the frame follow the work roll chocks, and the two cushions are supplied with fluid pressures depending on the moment of rotation produced from the difference in pressing reaction of the grinding member held in contact with a work roll at both the frame ends, thereby balancing the moment of rotation (hereinafter referred to as sixth prior art).